Anyone may post solutions. Please note that by submitting a solution, you agree that its contents are to be released under a Creative Commons Attribution-Noncommercial 3.0 Unported license, like SICP itself, and you assert that you have the right assign this license (i.e., that the solution is your own work). Leaving the title field blank will automatically generate a title based on the title of the exercise you are submitting a solution for. Unless you have a particularly exciting title in mind, this is usually the best choice. Solutions less than 10 words long will be automatically rejected.